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RADIOCHEMICAL INVESTIGATIONS ON NATURAL MINERAL

WATERS FROM BUCOVINA REGION, ROMANIA

MARIAN ROMEO CALIN1, ILEANA RADULESCU1, ALINA CATRINEL ION2,

FLORINELA SIRBU3

1Horia Hulubei National Institute for Physics and Nuclear Engineering-IFIN HH, Department of Life and

Environmental Physics, 30 Reactorului Str., P.O. Box MG-6, 077125, Bucharest–Magurele, Romania 2 University Politehnica of Bucharest, Department of Analytical Chemistry and Environmental

Engineering, 6 Polizu, Str. No. 1–7, 011061, Bucharest, Romania 3Ilie Murgulescu Institute of Physical Chemistry of the Romanian Academy, 202 Splaiul

Independentei Str., 060021, Bucharest, Romania

Received September 24, 2015

The access to a safe drinking water is essential to human health. In this respect,

the major ion composition, electrical conductivity and pH of nine natural mineral

drinking waters were studied. The waters originate from a volcanic aquifer containing

carbonate rocks, situated in northern part of Romania. It was found that the low

permeability of the aquifer allows a reduced infiltration of the rain water, seasonal

influence showing good chemical stability, oscillating around less than 10%.

Correlations were found between Ca2+, Mg2+ and HCO3– for both carbonated and non-

carbonated natural mineral water sources. In addition, an assessment of dose and risk

resulting from consuming these waters has been also performed. Gross alpha, gross

beta and radionuclides of natural decay chains 238U, 232Th, 226Ra and 40K activity

concentrations were measured, and the associate effective doses for these

radionuclides were determined. The results for the effective doses calculated for an

adult member of the public in Romania derived from the intake of naturally occurring

radionuclides in these waters vary between: 0.32–1.87 (µSv/yr) for 40K; 0.82–1.56 for 238U; 1.10–12.25 (µSv/yr) for 232Th and 4.49–32.70 (µSv/yr) for 226Ra. Based on this,

these waters can be recommended for regular consumption by infants and children,

too. This assessment on natural mineral water springs from the Bucovina region

updates data on the activity concentrations and effective doses due to intake of natural

radionuclides from drinking water in Romania.

Key words: ground water, major ion composition, activity concentration,

radionuclides, gross-α and gross-β, effective dose.

1. INTRODUCTION

The access to a safe drinking water is essential to human health [1]. The

European Union (EU) recognizes about 1000 brands [2] of natural mineral water and

its directives emphasize that bottled natural mineral water must be groundwater,

providing information about regional geology, characterized by its mineral content,

trace elements or other constituents and, where appropriate, by certain effects and be

clearly distinguishable from other ordinary drinking water [3–5].

Rom. Journ. Phys., Vol. 61, Nos. 5–6, P. 1051–1066, Bucharest, 2016

https://www.researchgate.net/institution/Romanian_Academy/department/Institute_of_Physical_Chemistry_Ilie_Murgulescu

https://www.researchgate.net/institution/Romanian_Academy

1052 Marian Romeo Calin et al. 2

The EU has already regulations for action levels for trace elements in bottled

water [6–8]. According to EU Directive 80/777/EEC, natural mineral waters are

defined as uncontaminated waters from underground aquifers [9], its chemical

composition resulting from chemical processes under natural conditions and

reflecting the mineralogical composition of the rocks. In this respect, the major ion

composition, electrical conductivity and pH of nine natural mineral drinking waters

are presented in this paper, on samples collected on long period of time (2.5–3

years) to study the chemical stability of these waters. For example, the higher

dissolved uranium concentration is associated with carbonate and bicarbonate

content, due to complexation [10]. In these conditions, radium behaves differently,

by precipitating with carbonates.

The paper presents data for the activity concentrations of 238

U, 232

Th, 226

Ra

and also for 40

K in nine carbonated and non-carbonated mineral waters. The study

evaluated the levels of natural radionuclides and chemical components, their

determination in ground water being useful as a direct input to environmental and

public health studies. Considering the high radiotoxicity of 226

Ra, its presence in

water and the associated health risk requires particular attention. An assessment of

the annual effective doses received from mentioned radionuclides is made, the

gross α and β activities in waters being measured for screening purposes.

According to WHO guidelines, the recommended screening levels for drinking

water below which no further action is required, are 0.5 Bq/L for gross alpha

activity and 1 Bq/L for gross beta activity [11].

This study further showed that radionuclides activity concentrations and thus

estimated annual effective ingestion doses assessed from natural bottled mineral

water consumption, whose locations are in different areas of Bucovina, vary

considerably. Since considerable amounts of natural mineral water are used in

Romania for drinking purposes, an extension of this survey to analysis of natural

mineral waters is needed to provide additional information and to get an overall

picture of the combined annual effective ingestion doses due to natural mineral

water consumption.

2. MATERIALS AND METHODS

2.1. CHEMICAL INSTRUMENTATION

The data set on the major ion composition of carbonated natural mineral

waters consists of samples from nine carbonated and non-carbonated natural

mineral waters, collected from the northern part of Romania called Bucovina

region. pH and electrical conductivity were firstly measured in 50 mL beakers,

filled with mineral water. The waters were monthly monitored and analyzed in 24

hours after sampling. Samples were filtered on 0.45 μm cellulose membrane filters,

the mineral components being analyzed by ion chromatography standardized

3 Radiochemical investigations on natural mineral waters from Bucovina region 1053

methods of analysis. Fluoride was measured using ion-selective electrodes, based

on a method previously developed in our group [12, 13]. Specific electric

conductivity (EN 27888:1993-11) and pH (DIN 38404-5:1984-01, C5) were

immediately analyzed after opening the bottles. Analytical method: IC standardized

method SR EN ISO 10304-1: 2009 IC standardized method SR EN ISO

14911:1999.

Stock standard ion solutions: 1000 mg/L are purchased as certified solutions,

or prepared from ACS 70 reagent grade, potassium or sodium, or other carbonate

salts.

All bottles were soaked in Milli-Q water, placed in an ultrasonic bath and

rinsed three times with Milli-Q water before use. An aliquot (20 mL) of the

samples was transferred into propylene vials and degassed for 30 minutes before

analysis. The instrument was calibrated weekly using external standards. A

regression fit value of over 0.995 was obtained for each element. Preparation and

analysis of samples, standards and blanks were carried out in triplicate. The method

detection limit (MDL) for the anions was calculated three times the standard

deviation of the signal of the blank sample analyzed 10 times [14]. Mineral water

samples are differently treated before analysis [15], depending on their

characteristics.

2.2. INSTRUMENTS FOR RADIOMETRIC MEASUREMENTS

Gross alpha–beta measurements were performed using the low background

system PROTEAN ORTEC MPC-2000-DP, with the following configuration:

scintillation radiation detector ZnS dual detector phosphor (zinc sulphide and

plastic), high power voltage; electronic modules for signal processing:

preamplifier, amplifier, counter; display module; operation and display control-

board equipped with LCD display; mechanical sample feeder; PC interface,

specialized software used for transferring acquired data and processing–PIC

Communicator–Protean Instrument Corporation. The system was calibrated

regarding its efficiency using sets of standard radioactive sources manufactured by

Radionuclide Metrology Laboratory (LMR IFIN-HH). One 241

Am–alpha source

(T1/2 = 432.6 ± 0.60 years) and of 90

(Sr-Y) – beta source (T1/2 = 28.80 ± 0.07 years)

were used. The working geometry used was fixed in metallic trays, inside the lead

castle system, directly facing the probe-detector for the measurement geometry UP

ALPHA + BETA manual count – the metallic tray being at 3 mm below the probe-

detector.

The calculated efficiencies of the detection were subsequently introduced in

the system for two working geometries: measuring geometry – gross alpha-beta =

= 31,37 ± 0.25 (%) – the alpha efficiency and = 44.94 ± 0.69 (%) – the beta

efficiency, where the spillover factor is = 25.59 ± 0.50 (%) and measuring

geometry up alpha – beta = 36.23 ± 0.29 (%) – the alpha efficiency and = 48.53 ±


± 0.74 (%) – the beta efficiency, where the spillover factor is = 31.08 ± 0.60 (%)

[16].

The samples were measured in 10 intervals of 100 min., the total acquisition

time being 16.6 h. In addition, a measurement with empty metallic tray for this

geometry was performed to establish the background count rate.

A low background coaxial p-type HPGe detector (model GEM 25P4) with a

relative efficiency of 35% and energy resolution of 1.73 keV at 1332.5 keV for 60

Co is used for determining the activity concentrations of the 40

K, 238

U, 232

Th and

their progenies. The detector, used for environmental radiation measurements, has

a Germanium crystal with a diameter of 59.1 mm and a length of 54.1 mm,

corresponding to a volume and mass of active Germanium of 148 cm3 and 0.8 kg,

respectively. The detector is linked to a DigiDART, Ortec data acquisition system

and to a Gamma Vision spectrum analysing software tool.

The calibration of the detector for energy, peak shape and efficiency was

carried out using certified volume sources for 60

Co, 134

Cs, 137

Cs, 152

Eu and 241

Am,

supplied by the institute’s radiation metrology laboratory. These radioisotopes

cover a relatively wide energy range (from 59.54 keV for 241

Am to 1408.00 keV for 152

Eu) and allow the construction of an empirical efficiency curve versus the energy

of interest (from 46.54 keV for 210

Pb to 2614.53 keV for 208

Tl) [17]. A 10 cm

thickness lead shielding and 2 mm of copper lining is built around the detector to

diminish the contribution of environmental radioactivity to its background.

3. RESULTS AND DISCUSSION

3.1. CHEMICAL ANALYSIS RESULTS

For the water samples, the concentration of main ions (Ca2+

, Mg2+

, Na+, K

+,

HCO3–, SO4

2–, Cl, F

– and NO3

–), electrical conductivity and pH are determined

being very important as a compositional fingerprint characteristic to the local

geology and to the position of the aquifer. The original geological description of

these of these mineral waters consists of dolomite and calcite containing traces of

quartz, muscovite, biotite, goethite and limonite [18]. In the aquifer, the principal

chemical reactions mainly involve the ions: Ca2+

, Mg2+

and HCO3–:

CaMg(CO3)2 + H2O- Ca2+

+ Mg2+

+ 2HCO3–

(1)

CaCO3 + H20- Ca2+

+ HCO3–+ HO

– (2)

The natural mineral waters presented in this study (Fig. 1) have

mineralization as shown by the electrical conductivity measurements which range

from 290 to 1883 μS/cm (for non-carbonated and carbonated, respectively). Major

ion components including statistical measures are presented in Table 1.


ROMANIA NORTH

Hungary

Bulgaria

Serbia

Ukraine

Moldova

BlackSea

Fig. 1 – Investigated test area on Romania’s map.

The chemical analyses of the nine investigated waters indicate that elemental

concentrations of Sb, Ni and Cu, expressed in micrograms per liter (µg/L) are in

the range 0.1–0.5 µg/L, 0.1–20, 1–80, respectively. The Mn values are 1–2 µg/L

for non-carbonated waters and > 0.5 mg/L before Mn removal for the carbonated

one.

Table 1

Mineral waters chemical data: mean values of pH, electrical conductivity and major ion composition,

analyzed each month (in triplicate), for three years

Source pH C.e.µ

(S/cm)

Cl

(mg/L) 2

4SO (mg/L)

3HCO

(mg/L)

2Ca

(mg/L)

2Mg

(mg/L)

Na

(mg/L)

K

(mg/L) 2O

Diss. 2CO

free

NO3-

(mg/L)

Dry rez.,

(mg/L)

MW1 6.13 1672 3.54 21.03 1220.2 267.25 67.0 5.02 2.48 2.43 1320 <0.1 1018.0

MW2 7.91 351.0 0.71 7.82 225.7 50.75 16.0 0.54 1.19 10.53 3.96 0.67 185.0

MW3 7.97 352 1.06 11.60 213.5 49.60 16.40 0.78 0.69 10.20 3.30 6.44 186

MW4 7.88 334.0 0.71 11.11 204.4 47.40 14.60 0.82 1.25 9.88 3.52 3.49 171.0

MW5 7.85 313.0 0.71 10.74 195.2 42.90 15.80 0.55 0.45 10.37 3.30 1.86 164.0

MW6 7.83 325,0 1.06 10.0 198.3 48.12 12.70 0.90 0.74 9.56 3,30 3.92 168.0

MW7 7.83 291.0 0.71 10.28 173.8 41.95 11.10 1.04 0.71 10.04 3.52 1.84 150.0

MW8 7.83 314 1.06 11.93 195.2 49.40 12.50 0.95 0.43 10.37 4.4 3.95 191.0

MW9 7.74 305 1.06 10.24 195.2 43.50 15.60 0.54 0.57 10.29 4.4 2.17 187.0

From the data it can be observed that the pH varies in the range 6.13–7.91, in

correlation with the CO2 from the aquifer, which contributes to the slightly acidic

character of the spring. The dissolution of primary minerals is limited and the

carbonation of water may lower the pH by 1–2 units transforming the CO2 in

HCO3–. The groundwater composition is dominated by HCO3

–, as well as by Ca

2+


and Mg2+

, as reflected by the values of the electrical conductivity. The studied

natural carbonated and non-carbonated mineral waters are Ca-Mg-HCO3–

ones, the

correlation between the HCO3– (mg/L) versus conductivity for the dataset depict

the contribution of HCO3– to groundwater chemistry. The conductivity values are

related to total dissolved solid of this natural mineral water (Fig. 2).

Fig. 2 – Conductivity values versus total dissolved solid of natural mineral water.

SO42–

present in the samples shows that the composition is influenced by a

volcanic contribution explained by the SO42–

enrichment by oxidation of reduced S

species from volatile releases. The main source of the sulphate ions present in the

chemical composition of the studied water is the rain, the aquifer itself containing

no sulphates in its geochemical composition. The important spread of SO42–

concentrations could shows a possible connection with the seasonal temperatures.

The alkali metals present are randomly correlated with HCO3–, the data

depicting a large excess of HCO3– in relation with Na

+ and K

+. The data suggests

mineralization processes specific to carbonate rocks, but also it indicates that a part

of the HCO3– is derived from the CO2 in the soil. The enrichment in alkalis may be

attributed to silicate weathering, which also contributes to increased HCO3–

content. It was observed a correlation between the K+

concentration and the beta

activity, because 40

K significantly contributes to the gross beta activity.

In contact with the carbonate rocks, the water will partially dissolve them,

high concentrations of Ca2+

, Mg2+

and HCO3– being specific to their chemical

compositions. The relation between alkali-earth and HCO3– shows a dependence

suggesting a basic rock aquifer reach in Ca2+

, Mg2+

and HCO3– species and a

stronger correlation between their concentrations. All the samples display Mg2+

contents above 10% of the cations, but the dominant one remains Ca2+

, the ratio

between these two cations being always constant. The greater release rate of Ca2+


compared to Mg2+

is a function of the calcite component of the carbonates which

would preferentially dissolve over dolomite [19]. The greater length of the Ca-O

bond in comparison with the Mg-O one makes the release of Ca2+

energetically

favorable [20], this being more common in natural systems. The higher dissolved

uranium concentration in underground waters is associated with HCO3–

content,

uranium presenting a higher solubility based on complex formation with

carbonates. The correlation between the gross alpha activity and the HCO3–

concentration gave no significant results, future investigation being necessary.

The presence of alkali and alkali-earth metals does not correlate between

each other, consistent with the high water mineralization. The water of the spring

has short residence time, involving a high water-rock ratio, with almost no effect of

silicate hydrolysis. In comparison with Ca2+

and Mg2+

concentrations, the

concentrations of Na+ and K

+ are less important, K

+ content being less than 2 % in

all samples, due to the weathering of silicate and to the high content of CO2 of the

water infiltrating into the aquifer for carbonated sources [21–23]. Zn2+

present in

the studied mineral waters in a range of concentrations 0.02–0.05 mg/L alters the

dissolution rate as well as the ratio of release of Ca2+

to Mg2+

and the application of

rate constants to natural systems in comparison with the synthetic ones with a

simplified aqueous chemistry [24, 25].

3.2. RADIOMETRIC ANALYSIS RESULTS

The activity concentrations for gross alpha, gross beta, annual effective

doses and radionuclides are presented in Tables 2–5. These ranges between 0.40

mBq/L and 45.40 mBq/L for gross-alpha, 1.51 mBq/L and 47.45 mBq/L for gross-

beta activities. The results obtained for gross alpha-beta measurements provide

basic information for consumers and competent authorities concerning the internal

exposure risk due to drinking water intake. It also represents a basis for comparison

when the dose contribution from artificial radionuclides released to the

environment as a result of any human practices and accidents in the studied area

are evaluated. It was observed that it is a poor correlation between the total

dissolved solids and the dissolved alpha activity, even if the samples belong to the

same aquifer.

The results obtained for total effective doses, taking into account the measured

radionuclides in all the analysed natural mineral waters are in the range of: 17.58–

33.95 µSv/yr with a mean value of 23.02 µSv/yr in 2012; 2.37–47.37 µSv/yr with a

mean value of 20.20 in 2013; 3.68–15.45 µSv/yr with a mean value of 8.36 in 2014

(Table 2). All values are well below the reference level of the committed effective


dose (100 µSv/yr) recommended by the WHO [11]. For more accurate dose

evaluation, the doses from some other important alpha and beta emitters, such as

radon should also be included.

Table 2

The activity concentration for gross alpha, gross beta and annual

effective dose for natural mineral water samples

nd: not determined.

Figures 3–5 show comparative results obtained in the case of the above

mentioned radionuclides [26–42]. The range of activity concentrations starts from

few mBq/L or detection limit up to a bit more than 1 Bq/L in case of 40

K (Fig. 3)

and 226

Ra (Fig. 5), while for 238

U this has very low values of a few mBq/L or

detection limit up to few hundreds of mBq/L (Fig. 4). Other reported values of 226

Ra activity concentrations in drinking water samples were up to 1.37 Bq/L in

[33], since for 238

U values up to 0.103 Bq/L were measured in [27]. In the case of 232

Th, there aren’t many reference values reported in the scientific literature, so

comparative data are not presented. However, the reported values for 232

Th in for

drinking water are comparable to the values reported in [28].

Sample

code

Residue

[g/L]

Gross Alpha

[mBq/L]

Gross Beta

[mBq/L]

Annual Effective Dose

DEFF[µSv/year]

Year 2012-2014 2012 2013 2014

MW1 1.0007 30.93 ± 2.41 1.84 ± 0.08 33.95 47.37 15.45

MW2 0.1963 2.10 ± 0.76 7.45 ± 1.40 17.97 13.86 5.44

MW3 0.1871 0.40 ± 0.20 4.80 ± 1.40 nd nd 8.98

MW4 0.1872 4.05 ± 1.70 47.45 ± 18 22.53 6.45 6.54

MW5 0.1821 2.35 ± 1.05 16 ± 2.18 nd 12.01 9.05

MW6 0.1428 5.30± 2.60 4.80 ± 1.40 nd nd 9.35

MW7 0.1515 1.55 ± 0.41 12.9 ± 3.14 nd 19.22 3.68

MW8 1.5370 45.40 ± 5.50 5.28 ± 0.34 nd 40.06 nd

MW9 0.2886 17.10 ± 7.80 1.51 ± 0.70 nd 2.37 nd

Mean

± 1σ 0.3866 12.13 ± 5.49 11.34 ± 4.08 23.02 20.20 8.36

Range 0.1428 –

1.0007 MDA – 45.40 MDA – 47.45

17.58–

33.95

2.37–

47.37

3.68–

15.45


Austria [36] Italy [27] Poland [29] Romania [32] Spain [30] Turkey [33]

0

500

1000

1500

2000

2500

40

K

Acti

vit

y c

on

cen

trati

on

(m

Bq

/L)

Fig. 3 – 40K activity concentrations range in natural mineral water.

Aust

ria

[36]

Aust

ria

[31]

Cro

atia

[39

]

Fin

land [40

]

Ger

man

y [3

5]

Gre

cee

[38]

Hungar

y [3

7]

Ital

y [2

6]

Ital

y [2

6]

Pola

nd [29

]

Rom

ania

[32

]

Slo

venia

[34

]

Turk

ey [41

]

0

50

100

150

200

250

300 238

U

Acti

vit

y c

on

cen

trati

on

(m

Bq

/L)

Fig. 4 – 238U activity concentrations range in natural mineral water.


Aus

tria [3

6]

Aus

tria [3

1]

Cro

atia [3

9]

Finl

and

[40]

Ger

man

y [3

5]

Gre

cee [3

8]

Hun

gary

[37]

Italy [2

7]

Italy [2

6]

Polan

d [2

9]

Rom

ania [3

2]

Slove

nia [3

4]

Spain

[30]

Turk

ey [4

1]

0

200

400

600

800

1000

1200

1400

1600

226

Ra

Acti

vit

y c

on

cen

trati

on

(m

Bq

/L)

Fig. 5 – 226Ra activity concentrations range in natural mineral water.

For the total annual effective dose calculation, (DEFF) equation 3 was used:

DEFF = (3)

where: DEFF is the annual effective ingestion dose due to relevant radionuclide in

μSv/yr, Ci is radionuclide activity concentration in the water sample in Bq/L, K is

the annual consumption rate of 150 L/yr for infants, 350 L/yr for children and 500

L/yr for adults, respectively, according to the ICRP, IAEA, WHO and UNSCEAR

[11, 44–45], Fi is the dose coefficient (conversion factors: 2.8×10–7

, 2.3×10–7

,

4.5×10–8

and 6.2×10–9

Sv/Bq for 226

Ra, 232

Th, 238

U and 40

K of the relevant

radionuclide for each age group given in the International Basic Safety Standards

for Protection against Ionizing Radiation and for Safety of Radiation Sources). In

the calculation of the total effective doses, per member of the public in Romania,

resulting from intake of naturally occurring alpha or beta radionuclides in drinking

water has been considered an average consumption of 1 litre per day × 365 days,

and the Fi coefficients.

Table 2 presents the amount of residue remaining after evaporation (slow

evaporation) of 5 L of water, too. The amount of residue after evaporation is higher


for MW1 sample than for other mineral natural water samples, this first sample

being mineral natural carbonated water.

Table 3 presents the activity concentrations of 40

K, 238

U, 232

Th and 226

Ra in

the residue of the water samples for the time interval 2012–2014. It can be

observed the activity concentration values for 40

K is in the range of 0.14–0.87

Bq/L, for 238

U of 0.050–0.17 Bq/L, for 232

Th of MDA-0.047 Bq/L and for 226

Ra of

MDA-0.32 Bq/L (Table 4).

Regarding the variation of activity concentrations (Tables 2 and 3) of water

samples analysed, this is fairly constant for the three years. However, it can be

noticed in the results of gross alpha, gross beta, and gamma spectrometry analyses

a slight decrease with time. As can be observed from Table 3, the measured activity

concentrations of 232

Th on water samples are in many cases extremely low, below

the minimum detectable activity (MDA) of the system used in the laboratory. The

same can be observed in Table 4 for the average of total effective doses of adult

member of the public.

Table 3

The activity concentrations of 40K, 238U, 232Th and 226Ra

in the residue of the water samples

Sample

code 40K [Bq/L] 238U [Bq/L] 232Th [Bq/L]

226Ra

[Bq/L]

Year 2012–2014

MW1 0.77 ± 0.09 0.086 ± 0.010 0.020 ± 0.003 0.28 ± 0.03

MW2 0.60 ± 0.06 0.095 ± 0.011 0.008 ± 0.001 0.09 ± 0.02

MW3 0.14 ± 0.03 0.070 ± 0.008 0.036 ± 0.004 0.044 ± 0.005

MW4 0.57 ± 0.06 0.081 ± 0.007 0.013 ± 0.002 0.09 ± 0.02

MW5 0.35 ± 0.04 0.064 ± 0.007 <0.37 (MDA) 0.09 ± 0.04

MW6 0.27 ± 0.03 0.09 ± 0.01 <0.03 (MDA) 0.07 ± 0.01

MW7 0.27 ± 0.03 0.050 ± 0.006 <0.37 (MDA) 0.11 ± 0.01

MW8 0.87 ± 0.08 0.088 ± 0.010 0.047 ± 0.005 0.32 ± 0.03

MW9 0.61 ± 0.06 0.060 ± 0.005 <0.28 (MDA) <0.20 (MDA)

Range 0.14–0.87 0.050–0.095 MDA –0.047 MDA –0.32

Mean ± 1σ 0.51 ± 0.10 0.085 ± 0.02 0.025 ± 0.005 0.14 ± 0.04

Table 4 shows the total effective doses per each years for an adult member

of the public in Romania resulting from intake of naturally occurring alpha or beta

radionuclides (40

K, 238

U, 232

Th and 226

Ra) in drinking water. The mean effective

doses (Table 3) are: 0.32–1.87 (µSv/yr) for 40

K; 0.82–1.56 for 238

U; 1.10–12.25

(µSv/yr) for 232

Th and 4.49–32.70 (µSv/yr) for 226

Ra.


Table 4

Total effective doses for an adult member of the public in Bucovina-Romania resulting from intake of

naturally occurring alpha or beta radionuclides in natural mineral water

Table 5 presents the analysis of the dose contribution fractions from

potassium, uranium, thorium and radium. The dose contribution fractions of the

analysed water samples are in the following order: 12.11 % from potassium, 13.01

% from uranium, 19.07 % from thorium and 72.32 % from radium.

The higher contribution ratios of 226

Ra are connected to the higher water

solubility of radium than its thorium and uranium precursors [46–47]. 226

Ra is a

radiotoxic radionuclide which can be adsorbed in soft tissues and bones. For 226

Ra

the measured values are not higher than in other European countries, such as

Hungary, Poland and Spain, as it can be observed from Fig. 5.

Table 5

Analysis of the dose contribution fraction from: potassium, uranium, thorium and radium

Sample

code

Dose fraction

from40K (%)

Dose fraction

From 238U (%)

Dose fraction

from232Th (%)

Dose fraction

from226Ra (%)

MW1 3.79 3.23 27.87 65.12

MW2 9.85 11.38 14.08 64.70

MW3 3.49 12.55 34.93 49.01

MW4 10.18 11.75 8.61 69.46

MW5 7.50 9.96 nd 82.54

MW6 6.52 15.82 nd 77.64

MW7 5.01 6.74 nd 88.25

MW8 4.68 3.63 9.88 81.81

MW9 57.98 42.02 nd Nd

Mean 12.11 13.01 19.07 72.32

nd: not determined

Sample

code

Mean 40K

[µSv/yr]

Mean 238U

[µSv/yr]

Mean 232Th

[µSv/yr]

Mean 226Ra

[µSv/yr]

Year 2012–2015

MW1 1.66 1.42 12.25 28.62

MW2 1.35 1.56 1.93 8.87

MW3 0.32 1.15 3.20 4.49

MW4 1.30 1.50 1.10 8.87

MW5 0.79 1.05 nd 8.70

MW6 0.61 1.48 nd 7.26

MW7 0.61 0.82 nd 10.74

MW8 1.87 1.45 3.95 32.70

MW9 1.38 1.00 nd Nd

Range 0.32–1.87 0.82–1.56 1.10–12.25 4.49–32.70


Table 6

Dose coefficients Fi of the relevant radionuclides in (nSv/Bq) for three age groups

Age group 238U 232Th 226Ra 40K

1–2 years 120 450 960 42

2–7 years 80 350 620 21

7–12 years 68 290 800 13

12–17 years 67 250 150 7.6

>17 years 45 230 280 6.2

In the calculation of the total effective doses, per member of the public in

Romania, resulting from intake of naturally occurring alpha or beta radionuclides

in drinking water has been considered an average consumption of 1 litre per day ×

365 days, and the Fi coefficients given in Table 6.

4. CONCLUSIONS

Chemical and radiochemical characterization of nine natural mineral

carbonated and non-carbonated waters was performed. Samples were collected

during three years in order to identify the trends of the chemical and radiochemical

evolution. The evaluation with time over the chemical composition of the studied

mineral water shows good chemical stability oscillating around less than 10%. It

was also observed that the low permeability of the aquifer allows a reduced

infiltration of the rain water. In the aquifers containing carbonate rocks, the waters

present higher concentrations of alkali-earth metals in correlation with HCO3–,

which is less correlated with the reduced amounts of Na+ and K

+ from these rocks,

but well-correlated with uranium and radium solubility in radiometric analysis.

The content of natural radionuclides such as 40

K, 238

U, 232

Th and 226

Ra in

these natural mineral waters has also been investigated, showing that natural

radioactivity levels vary in a broad range. The 226

Ra radionuclide content varies

from 0.07 Bq/L to about 0.32 Bq/L. The 226

Ra radionuclide, with a half-life of 1630

years, can supply important scientific information concerning mechanisms and

rates of water–rock interaction and transport of this element in aquifers. The 232

Th

isotopes content varies from 0.008 Bq/L to about 0.047 Bq/L, 40

K between

0.14–0.87 Bq/L and 238

U of 0.050–0.095 Bq/L. The results obtained are very well

in agreement with those reported in many European countries, as was shown in

Figs. 2–4. The results obtained for the total effective doses for an adult member of

the public in Romania resulting from intake of naturally occurring alpha or beta

radionuclides in natural water, are: 0.32–1.87 (µSv/yr) for 40

K,0.82–1.56 for 238

U,

1.10–12.25 (µSv/yr) for 232

Th and 4.49–32.70 (µSv/yr) for 226

Ra. Taking into

account the measured radionuclides listed above, the mean annual effective doses

for all the analysed drinking water samples are in the range of 2.37–47.37 µSv/yr


(Table 3), all being well below the reference level of the committed effective dose

(100 µSv/yr) recommended by the WHO.

Relatively small variations of the concentrations of 226

Ra, 232

Th and 40

K from

one spring to another for these natural mineral carbonated and non-carbonated

water samples at the Bucovina area indicate that the origins of these waters are the

same, but that they could come from different depths and may pass through slightly

different geological layers. The application of radiometric spectrometry methods

for determination of both radionuclide activity give valuable information

concerning mutual transportation between surface, subsurface and deeply situated

natural mineral water layers.

The surveillance of the natural mineral waters has to be done continuously to

get consistent data with international rules. Analyses done on samples of natural

waters are in good agreement with the Directive 2009/54/EC of the European

Parliament. The obtained data can provide basic information for consumers and

competent authorities to be aware of the actual problem of radiation. Records on

the activity concentrations and effective doses due to intake of natural

radionuclides from natural mineral water must be updated as some of the data are

older than 20 years. In all these last 20 years many suppliers of natural mineral

water have appeared on the market and more important new springs are in used.

Acknowledgments. This study was supported by the PNCDI II Program, Project No. PN 09 37

03 01/2014 and 2015, by the Romanian Ministry for Education and Research.

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